The NSA has proposed a FOIA exemption for “files that document the means by which foreign intelligence or counterintelligence is collected through technical systems.” Also via FAS, see the text of the proposed exemption, the National Defense Authorization Act for Fiscal Year 2004, S. 747.
From OMBWatch, “The Senate language, included in the proposed FY 2004 Defense Authorization Act (S. 1050, sec. 1035), would exempt all “operational files” of the NSA from public disclosure under the Freedom of Information Act (FOIA). “